DOCS: Fix examples in documentation (#1435)

* Add example include

* Replace example includes

* Remove old example includes

docs/_functions/domain/MX.md

@@ -13,13 +13,13 @@ Priority should be a number.
 
 Target should be a string representing the MX target. If it is a single label we will assume it is a relative name on the current domain. If it contains *any* dots, it should be a fully qualified domain name, ending with a `.`.
 
-{% include startExample.html %}
-
+{% capture example %}
 ```js
 D("example.com", REGISTRAR, DnsProvider(R53),
   MX("@", 5, "mail"), // mx example.com -> mail.example.com
   MX("sub", 10, "mail.foo.com.")
 );
 ```
+{% endcapture %}
 
-{% include endExample.html %}
+{% include example.html content=example %}